Ubuntu 12.10 neither shuts down nor reboots properly

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http://askubuntu.com – (HP dv6-6180eg, Intel3000/ATI 6770M) Although there have been several questions posted about this issue, I'm still not able to find a solution. FYI, it's not possible to toggle the screen brightness out of the box on my dv6, so therefore I added those lines to my grub file: (seen here) GRUB_CMDLINE_LINUX_DEFAULT="splash acpi_backlight=vendor" GRUB_CMDLINE_LINUX="acpi_backlight=vendor" I deleted them, and it worked! But now I can't toggle my screen brightness anymore. Therefore I tried this. It still doesn't work. Any solution? Thanks in advance! (HowTos)